fluorescent tube and circline lamp

Fluorescent tube lamps – the second most popular type of lamps –
are more energy efficient than the more popular A-type standard
incandescent lamps.

The traditional tube-type fluorescent lamps are usually identified as T12
or T8 (12/8 or 8/8 of an inch tube diameter, respectively). They are installed
in a dedicated fixture with a built-in ballast. The two most common types
are 40-watt, 4-foot (1.2-meter) lamps, and 75-watt, 8-foot (2.4-meter) lamps.

Tubular fluorescent fixtures and lamps are preferred for ambient lighting
in large indoor areas. In these areas, their low brightness creates less
direct glare than incandescent bulbs.

Circular, tube-type fluorescent lamps are called circline lamps.
They are commonly used for portable task lighting. See also compact
fluorescent lamp.